The present invention relates to a connection apparatus and particularly, but not exclusively, to a double shoulder high torque connection used to connect tubular members in a drill string such as tubular members that connect together to form the outer housing of a downhole tool.
Threaded connection joints such as tapered pin and box joints are used widely in the drilling industry to allow a series of tubular members and components, which make-up downhole tools and which are connected on the drilling rig, to form a drill string for insertion into the borehole.
Standard connection joints for drill strings may include a tapered male member (pin) on the lower end of one tubular member that may be inserted into a tapered female member (box) on the upper end of another tubular member such that a single shoulder is provided into which a reasonable amount of torque can be applied. However, the weakness created in the drill string at the drill pipe and tool component connections has the disadvantage of creating deformation of the joint and/or drill string when a large torsional load is placed upon it.
In recent years it has become known to use tapered thread double shoulder connections in drill pipe joints, such as the eXtreme™ Torque Connection XT™ drill pipe tool joint offered by Grant Prideco of Houston, Tex., USA, which allow higher levels of make-up torque to be applied to the drill pipe connections, which are required for extended reach and/or horizontal drilling and other extreme drilling applications. However, hitherto, it has been impossible to provide similarly high levels of make-up torque to downhole tool component connections. Hence, conventional downhole tool component connections constitute low torque connections, which denigrate the torque rating of the whole drill string.
What is needed, therefore, is an apparatus and a methodology that address at least one if not more of the deficiencies that afflict conventional practice, as previously described.